In the field of vehicle development, more and more interest is being focused on vehicles that can operate automatically without a driver. Automatic guided vehicles are used extensively in material handling, and there is keen interest in developing them for a range of other uses which is limited only by the imagination. A means for guiding such vehicles along a desired course is a first requirement.
The use of a fixed guideway is currently the most common technique. A signal-carrying wire may be buried in the floor and the vehicle made to follow it by on-board inductive coils. Such systems work well but are expensive to install or re-route. Sometimes a reflective stripe is painted on the floor and the vehicle is equipped with a photoelectric device to sense the stripe and direct the vehicle to follow it. These systems work also, but the floor stripes are subject to wearing off by traffic, which degrades the performance of the system, and they are inconvenient to re-route.
A recent trend is toward guiding a vehicle with a laser beam. Typically a laser-emitting unit is mounted on the vehicle, and its beam is reflected back to the vehicle from established targets in known locations to provide the information needed to guide the vehicle. Such a system is described in U.S. Pat. No. 4,647,784, for example. But while laser systems eliminate fixed guideways, they still require the installation of special targets. This entails some expense and inconvenience when installing or relocating them, and the targets may not be aesthetically appealing.
A preferred approach is an unmanned vehicle equipped to guide itself along a selected route without the need to install guideways or targets or any other special equipment in its work area. Ideally it would be able to guide itself by referring only to pre-existing features in its surroundings as landmarks. The present invention is an unmanned vehicle which guides itself by reference to overhead visual targets such as pre-existing overhead lights. Since overhead lights are universally found in commercial and industrial buildings, this vehicle when used in such buildings meets the need for an unmanned guidance system that does not require the installation of any special equipment in the work area.